Press and Publications Office
University of Leicester
Mass Extinctions -- A Threat from Outer Space or Our Own Planet's Detox?
University scientists suggest extraterrestrial theories are flawed and
that more down to earth factors could have accounted for past mass
Earth history has been punctuated by several mass extinctions rapidly
wiping out nearly all life forms on our planet. What causes these
catastrophic events? Are they really due to meteorite impacts? Current
research suggests that the cause may come from within our own planet --
the eruption of vast amounts of lava that brings a cocktail of gases
from deep inside the Earth and vents them into the atmosphere.
University of Leicester geologists, Professor Andy Saunders and Dr Marc
Reichow, are taking a fresh look at what may actually have wiped out the
dinosaurs 65 million years ago and caused other similarly cataclysmic
events, aware they may end up exploding a few popular myths.
The idea that meteorite impacts caused mass extinctions has been in
vogue over the last 25 years, since Louis Alverez's research team in
Berkeley, California published their work about an extraterrestrial
iridium anomaly found in 65-million-year-old layers at the
Cretaceous-Tertiary boundary. This anomaly only could be explained by an
extraterrestrial source, a large meteorite, hitting the Earth and
ultimately wiping the dinosaurs -- and many other organisms -- off the
Professor Saunders commented: "Impacts are suitably apocalyptic. They
are the stuff of Hollywood. It seems that every kid's dinosaur book ends
with a bang. But are they the real killers and are they solely
responsible for every mass extinction on earth? There is scant evidence
of impacts at the time of other major extinctions e.g., at the end of
the Permian, 250 million years ago, and at the end of the Triassic, 200
million years ago. The evidence that has been found does not seem large
enough to have triggered an extinction at these times."
Flood basalt eruptions are -- he says -- an alternative kill mechanism.
These do correspond with all main mass extinctions, within error of the
techniques used to determine the age of the volcanism. Furthermore, they
may have released enough greenhouse gases (SO2 and CO2) to dramatically
change the climate. The largest flood basalts on Earth (Siberian Traps
and Deccan Traps) coincide with the largest extinctions (end-Permian,
and end-Cretaceous). "Pure coincidence?", ask Saunders and Reichow.
While this is unlikely to be pure chance, the Leicester researchers are
interested in precisely what the kill mechanism may be. One possibility
is that the gases released by volcanic activity lead to a prolonged
volcanic winter induced by sulphur-rich aerosols, followed by a period
of CO2-induced warming.
Professor Andy Saunders and Dr. Marc Reichow at Leicester, in
collaboration with Anthony Cohen, Steve Self, and Mike Widdowson at the
Open University, have recently been awarded a NERC (Natural Environment
Research Council) grant to study the Siberian Traps and their
The Siberian Traps are the largest known continental flood basalt
province. Erupted about 250 million years ago at high latitude in the
northern hemisphere, they are one of many known flood basalts provinces
-- vast outpourings of lava that covered large areas of the Earth's
surface. A major debate is underway concerning the origin of these
provinces -- including the Siberian Traps -- and their environmental impact.
Using radiometric dating techniques, they hope to constrain the age and,
combined with geochemical analysis, the extent, of the Siberian Traps.
Measuring how much gas was released during these eruptions 250 million
years ago is a considerable challenge. The researchers will study
microscopic inclusions trapped in minerals of the Siberian Traps rocks
to estimate the original gas contents. Using these data they hope to be
able to assess the amount of SO2 and CO2 released into the atmosphere
250 million years ago, and whether or not this caused climatic havoc,
wiping out nearly all life on earth. By studying the composition of
sedimentary rocks laid down at the time of the mass extinction, they
also hope to detect changes to seawater chemistry that resulted from
major changes in climate.
From these data Professor Saunders and his team hope to link the
volcanism to the extinction event. He explained: "If we can show, for
example, that the full extent of the Siberian Traps was erupted at the
same time, we can be confident that their environmental effects were
powerful. Understanding the actual kill mechanism is the next stage ...
watch this space."
More information is available from the website:
Note to editors:
Further information is available from Professor Andy Saunders,
Department of Geology, University of Leicester, tel 0116 252 3923; or
from Dr Marc Reichow, email: mkr6 @ le.ac.uk .